Field of the Invention
This invention relates to controls for electric coffee makers, and in particular to a control module for manual switch-type automatic drip coffee machines.
Description of the Prior Art
In 1993, U.S. Pat. No. 5,183,998 (Hoffman et al., “the '998 patent”) was issued describing an automatic electric coffee maker or the like having user selectable AUTO, BREW, WARM or OFF states. The control used a triac to provide full power to brew the coffee, and reduced power which could be user adjusted to set the WARM temperature level. A temperature sensor could determine if the machine should be cleaned and to determine if the BREW state was complete and automatically convert to the WARM state, and to turn the machine OFF if the WARM temperature was too high.
The temperature sensor and the triac that were used posed several problems. The triac required a heat sink to dissipate the heat generated by the heater current. The triac could fail in a shorted condition that would require the thermal fuses to open and render the coffeemaker inoperable. The temperature sensor needed special mounting to react quickly enough to the heater temperature. The heater temperature control potentiometer could become dirty and cause erratic operation in the WARM state. The increased performance was offset by reliability and product cost issues.